Tuisto / Tuiscon / Tuisco
In "Germania," (section 2) Tacitus writes: 'They relate in ancient songs, which is the only historical tradition among them, that the god Tuisto was born from earth. They assign him a son, Mannus, the source and founder of the race, and to Mannus three sons, from whose names those nearest the oceans are called Ingaevones, those in the center Herminones, the rest Istaevones. Certain sources claim, as customarily happens with the license of antiquity, that the god had more offspring and that there were more designations of the people, Marsi, Gambrivii, Suebi, Vandilii, and that these are real and ancient names..."
The subject of a Germanic creation myth is complicated, though Grimm cites (pp. 564-576, particularly 567-569) some syncretic and post-conversion sources that paint some differences among the Continental Germanic creation understandings and the Scandinavian lore, and some of these differences are turning up in the oral lore of Braucherei and Hexerei. Just as an example, one stark difference that comes in our oral lore is that the race of the Zwarich (Dwarves) was created before the Giants and that the Zwarich have a role in helping to maintain order against the forces of chaos. Another difference is the reference to Wurt (Wyrd, though often other terms, especially "Schicksaal" are used for the same concept) as a maker force or personified as a deity, though whether the force is conscious, proto-conscious, or unconscious is not particularly clear.
Some theories within the Urglaawe community:
A relationship between Tuisto and Ewicher Yeeger based in part on the earth-sprung god aspect. I personally can see a relationship between Ewicher Yeeger and Ullr, but I am increasingly less inclined to see Tuisto and Ewicher Yeeger as the same deity.
A relationship between Tuisto and Ziu, based partially on linguistic conjecture or on a possible relationship of Tuisto being the son of Ziu. I am not so inclined toward this theory anymore.
Tuisto as an equivalent of Norse Buri and Mannus as the equivalent of Borr. This idea is hard to follow through, but it is worth exploring.
Tuisto and Ymir being two different perceptions of the same entity. Linguistically, there is a connection, though the viewpoints end up being quite different. In the case of Ymir, the body is taken apart to by the gods to create the universe whereas the notions associated with Tuisto are those of a proactive creator, regardless of consciousness level. As Grimm (568) states, "The main difference between the Scandinavian view and all the others is, as I said before, that the one uses the microcosm as material for the macrocosm, and the other inversely makes the universe contribute to the formation of man. There the whole of nature is but the first man gone to pieces, here man is put together out of the elements of nature." His exploration goes on well beyond that onto page 569, so it is an interesting section for this topic.
Tuisto, Ymir and Hindu Tvastar as perceptions of the same entity. This one I am increasingly buying into, particularly as some of the characteristics of Tvastar match the "maker" concept that turns up in our oral lore but is ascribed more to Wurt or Schicksaal than to a deity by name.
I am interested to hear what others know/think.